The text isn't useless. I describe the use

To me, the proposed "synopsis" is useless (given sub name, source, possibly with comment and/or pod, ctags).

More detailed documentation, where warranted, is in no way precluded by adding a synopsis.

Synopsis of a sub would already be listed at the beginning of the (sub) documentation.

As for the original purpose of searching files with synopsis, assuming POD which has sub name on =item line ...

# GNU egrep.
egrep -A 5 '^=item.+<sub name>' <file list>
[download]

... adjust N (= 5 above) to your liking. Whole thing can be easily wrapped so that one would need to supply only sub name regex & file names.